1. Field of the Invention
The present invention relates to a breathing monitoring device having a multi-point detector for monitoring the movement of the chest due to chest breathing and the movement of the abdomen due to abdominal breathing, using a determination means for determining a movement amount, mounted on a plurality of portions on a patient's body, which physically move due to respiration, to achieve highly accurate monitoring of a combined displacement amount of the patient's body due to respiration.
2. Description of the Related Art
In radio-therapy irradiation to or image capturing of a patient's body, using a CT (computer tomography system) device or a radio therapy system, the patient's target portion may remain unstable in position due to physical movement of his/her body due to respiration. This leads to a problem including deterioration in quality of a captured image, irradiation to normal tissues other than the treatment target portion, and so forth. In view of the above, conventionally, a so-called respiratory-gated technique (synchronization with respiration) is applied to electrically determine the amount of movement of the patient's body, using laser or infra-red radiation and to carry out image capturing and/or radio-therapy irradiation, using a signal in synchronism with the body movement.
However, according to a conventional respiration-gated technique, in which laser or infra-red radiation is applied to only one of the patient's chest and abdomen in determining the movement of his/her body, only either one of the lung and abdominal breathings can be subjected to determination. Moreover, determination of respiration-caused movement by means of laser or infra-red radiation uses a laser, an infra-red radiation sensor, or an electrical sensor, and also a calculation computer and an analogue circuit for signal processing the respiration-caused movement amount. This results in the device complicated and expensive.
In radio-therapy irradiation applied relative to a chest or an abdomen, for example, the patient is required to hold breathing for the purpose of reducing a PTV (or planning target volume), with various breathing holding methods available, and the irradiation is applied while monitoring the patient's respiration. However, as the monitoring relies on the information concerning only one of the chest and the abdomen, the ventilation amount in free breathing, in which abdominal breathing and chest breathing coexist, and the exact tumor position are not accurately reflected.
In a medical situation, a self breathing holding method using no breathing monitoring device is conventionally employed. However, review on the self breathing holding method shows extremely inferior accuracy in holding breathing by a patient with poor understanding of the self breathing holding method. In view of the above, development of a readily understandable breathing holding method and breathing monitoring device with high accuracy has been desired.